ARCH 524 Midterm Exam

percentage of solar radiaiton absorbed

operate on a cycle of storing and releasing heat, utilize direct solar gain to heat buildings, and examples are a trombe wall and a water wall.

insulative capacity of earth.

The Crack Length Method is more accurate than the Air Change Method.

.0393 because R-value = 1/U-value

IAQ = Indoor Air Quality

VOC - Volatile organic compound; particles, allergens, and agents of microbial origin

• 1. Dampness
• 2. Ventilation
• 3. Building Materials
• 4. Indoor Air Chemistry

• 1. Find balance between natural and man made environment.
• 2. Try to work with, not against the natural environment.
• 3. Need to be aware of and understand the site’s environmental conditions.
• 4. Study the environment first, design second.

a climate within a climate; in cities, cloudiness, relative humidity, contaminants, temperature, etc.

an indicator of how much energy must be invested to mine/harvest/produce, fabricate, and transport a unit of building material

condition of mind which expresses satisfaction with the thermal environment; influenced by temperature, humidity, air speed, materials of the building, number of windows, etc and is both psychological and physiological interaction

body wants to reach equilibrium with environment

• Bodies ability to retain/gain heat to achieve equilibrium with the environment
• M - metabolic rate
• E - rate of heat loss by respiration, evaporation, elimination
• R - radiation rate
• C - conduction and convection rate
• S - body heat storage rate

• Dry bulb temperature - temperature measured by an ordinary thermometer
• Wet bulb temperature - takes humidity into account

• 1. Metabolic Rate (met)
• 2. Clothing insulation (clo)
• 3. Air temperature
• 4. Radiant temperature
• 5. Air Speed
• 6. Humidity

“the uniform temperature of an imaginary surrounding enclosure in which radiant heat transfer from the human body would eqaul the radiant heat transfer in the actual nonuniform enclosure”; affects the rate of radiant heat loss from the body

according to ASHRAE, only 80% of occupants need to be satisfied with thermal comfort

experimentally determined index based on combination of dry bulb temperature, humidity, radiant conditions, and air movement

based on dry-bulb temperature and humidity

if a change occurs such as to produce discomfort, people react in ways which tend to restore their comfort; little impact on performance

flow of heat-energy transfer between 2 regions due to a difference in temperature (from hot to cold)

• 1. magnitude of temperature difference
• 2. area perpendicular to heat flow path
• 3. resistance to heat transfer

a traditional unit of energy equal to 1055 joules

energy required to raise 1 pound of a material 1 degree Fahrenheit

• capacity of a material to store energy
• HEAT CAPACITY = SPECIFIC HEAT x DENSITY x VOLUME
• or
• SPECIFIC HEAT x WEIGHT

• E = Energy gained/stored (Btu)
• HC = heat capacity (Btu/lb⃙F)
• ᐃT = change in temperature (⃙F)

• (necessary for calculation of building envelope heat gain/loss)
• * want a HIGH R value and a LOW U value *
• K (conductivity) - the rate of heat flow through a homogeneous material, per unit of thickness
• C (conductance) - rate of heat flow through a homogeneous material of a given thickness
• R (resistance) - a measure of resistance to the passage of heat
• R = 1/C (higher the R, more resistance to heat gain)
• U (overall coefficient of heat transmisison) - the overall rate of heat flow through any combination of materials (including air)
• U = 1/R

variance in temperature through a cross-section of a construction assembly; the temperature at any point within a wall, roof, or floor assembly can be predicted if the inside and outside air temperatures and thermal properties of construction are known

• M = mechanical heating or cooling
• I = internal gains
• S = solar heat gains
• T = transmission of heat through envelope (loss or gain)
• O = outdoor air load (heat loss or gain)

• 1. Conservation of Energy
• 2. Quality of energy

• Q=CFM 1.08 (Ti-To)
• Q = sensible load
• CFM = volume of infiltration
• 1.08 = outdoor air factor
• Ti-To = indoor air temp - outdoor air temp

• Air Change Method - if the AHC = 1, the entire volume of air in the room has been replaced by outdoor air in 1 hour; higher the number, higher the leakage
• Crack Length Method - more precise but requires much more specific information about dimensions and construction details of plan

• Sensible heat - transferred via conduction (must be physically touching); measured with thermometer (DRY BULB ONLY)
• Latent heat - change of state or phase change of a material (i.e. ice to water); takes both dry bulb temperature and humidity into consideration
• Radiation - exchange of radiant energy between 2 bodies across open surface

a material acts as a heat sink by absorbing heat and thus cooling a space; releases the heat later to warm the space

• 1. Mechanical Cooling
• 2. Passive Cooling
• 3. Heat Avoidance
• * START AT THE BOTTOM*

• A. Comfort ventilation (ventilate all day/night to increase evaporative cooling)
• B. Night flush cooling (pre-cool building for next day)

• A. Direct (roof surface cools by radiation at night)
• B. Indirect (use of heat-transfer fluid radiates - i.e. water)

• A. Direct (water sprayed into air entering)
• B. Indirect (location of site near water, pool in courtyard, etc)

• A. Direct (earth-sheltered building looses heat directly to earth)
• B. Indirect (air enters building by way of earth tubes)

removal of latent heat (humidity is always more uncomfortable than dry heat)

• - maximize air flow
• - operable windows
• - lightweight construction
• - windows open all the time

• - hot/dry climate
• - window or whole house fans should be used
• - airflow must be directed over mass

• - good in clear sky areas with low humidity
• - mainly one-story buildings
• - roof painted white UNLESS used for passive heating
• - whole roof area should be used because effect is small

- only dry climates

• - direct is best when earth’s temperature is < 60. If much colder, building needs insulation
• - earth tubes are good in dry climates with cold winters
• - underground structures have reduced access to natural ventilation (con)

• - uses chemicals to absorb water vapor
• - 2 difficulties: 1. when water vapor is absorbed and turned into a liquid, heat is given off 2. once desiccant is saturated, it stops removing humidity

• - surface color (light reflects, dark absorbs)
• - solar shading

position varies according to latitude, season, and time of day

• determined by position of sun
• Tlocal = Tsolar + [Longitude – Longituderef) x 4]

keep heat from entering building in the first place

water has higher capacity to hold energy than wood/stone

• 1. Air flows either because of natural convection current, caused by differences in temperature, or because of differences in pressure. Always from high to low pressure.
• 2. Conservation of air.
• 3.Air has mass ( and thus momentum) and it will tend to continue in its direction until altered by an obstruction of adjacent airflow.
• 4. The overall effect of wind at a site is so large that locally deflected airflow will tend to return to the direction and speed.
• 5. Laminar airflow is smooth with adjacent air moving in similar direction and speed. Slow, gentle alterations of flow direction preserve laminar flow, while abrupt alterations result in turbulent flow.
• 6.Bernoulii effect - an increase in the velocity of a fluid decreases its static pressure; velocity of air increases with height above ground; Result: air pressure at roof is lower than at ground level resulting in exhaust of air through roof openings
• 7. Venturi effect - causes an acceleration when laminar airflow is constricted in order to pass through an opening; if constriction is so abrupt to create turbulence, Venturi acceleration is minimized
• 8. High and low pressure areas - as air hits the windward side of a building, it compresses and creates a positive pressure. At the same time, air is sucked away from the leeward side, thus creating negative pressure.
• 9. Cross-ventilation requires an outlet as well as an inlet
• 10. Stack effect - can exhaust air by natural convection (because hot air rises)

induce heating of air to draw ventilation through building

• 1. Mechanical Heating
• 2. Passive Solar Heating
• 3. Heat Retention
• *START AT BOTTOM*

• 1. Maximize solar radiation
• A. southern exposure
• B. thermal storage
• 2. Avoid winter wind
• A. heat loss through convection
• B. infiltration
• 3. Buffer north exterior wall with less frequently used spaces
• A. bathrooms, storage, mechanical, etc.
• 4. Passively warm outdoor air before it enters space

collects and traps solar radiation during the day; glass allows short radiation to pass through and change to a long wavelength therefore it becomes traps and can no longer pass through

massive floors should be medium to dark in color while the finish of non-massive materials should be light

uninsulated wall operates by convection while insulated are fan assisted; air between glass and wall is heated, rises, and enters living space; has the ability to reduce building heating load by up to 35%

a wall built with a water surface is more efficient in storing heat than timber, stone, and brick

the greater the exposed surface area, the greater the rate of heat loss/gain

• - there are Heating DDs (HDD) and Cooling DDs (CDD)
• - refer to average daily temperature below or above a base temperature; each day’s mean temperature is subtracted from base temperature which equals the number of DDs for that day
• i.e. high: 70 F low 32 F = mean 51
• 60-51 = 9 HDD60
• - good for comparing buildings within a climatic region

• - health and well-being of building occupants
• - productivity
• - lawsuits
• - professional responsibility
• - 90% of time spent indoors

symptoms improve with time away from problem building and recur on return to building; temporary

illness brought on by exposure to building air where symptoms of diagnosable illness are identified and can be directly attributed to environmental agents in the air

• 1. Building materials
• 2. HVAC
• 3. Construction/design
• 4. Landscaping and site planning
• 5. Indoor equipment
• 6. People
• 7. Animals/insects

• - sustainable green design
• - space planning
• - avoid cross contamination of supply air
• - maintenance schedule
• - construction site maintenance
• - displacement